Certain filter materials have been suggested for incorporation into cigarette filters, including cotton, paper, cellulose, and certain synthetic fibers. However, such filter materials generally only remove particulate and condensable constituents from tobacco smoke. Thus, they are usually not optimal for the removal of certain gaseous constituents from tobacco smoke, e.g., gas phase constituents or volatile organic compounds. Also, certain materials when placed in cigarette filters will non-selectively remove constituents in mainstream tobacco smoke, and may thus yield a product with undesirable taste.
Further, certain materials remove constituents from mainstream smoke through chemical or catalytic reaction. For example, U.S. Pat. No. 6,119,699 describes certain functionalized silica or resin particles and U.S. Pat. No. 5,204,376 describes an anion exchanger that is functionalized with a specific diamine group. U.S. Pat. No. 4,202,356 describes a smoke filter containing an imidazole-containing polymer, where the imidazole groups are chemically bound to the polymer. U.S. Pat. No. 4,156,431 describes an unsulfonated cross-linked polystyrene. U.S. Pat. No. 4,059,121 describes a thermoplastic polymeric non-absorbent material. U.S. Pat. No. 4,033,361 describes a tobacco-smoke filter, which contains, as adsorbent for volatile tobacco-smoke constituents, a macroporous amine-type anion-exchange resin which contains substantially primary amino groups. U.S. Pat. No. 3,217,719 describes certain functionalized polymeric compounds that form a complex with phenol and phenolic compounds.
U.S. Pat. No. 4,700,723 describes certain tobacco filters with fibrous ion exchange resins, which are said to have ion exchange ability through the introduction of cation or anion exchange groups or chelating groups to polymers. Similarly, U.S. Pat. No. 4,226,250 describes a cation exchange material. U.S. Pat. No. 3,093,144 describes tobacco filters containing an ion exchange resin including aromatic groups, that are able to bind nicotine and the tarry constituents of tobacco smoke and U.S. Pat. No. 2,815,760 describes tobacco smoke filters for selective removal of certain constituents of mainstream smoke, which include ion exchange materials, along with other additional materials to chemically react with certain constituents of mainstream smoke. U.S. Pat. No. 2,754,829 describes filters containing an ion exchange material, such as a hydrogen exchanging cation exchanger. Other filters are described in U.S. Pat. Nos. 5,998,500; 5,817,159; and 5,570,707, as well as British Patent Nos. 1,100,727; 1,097,748; 908,185; 858,864; and 588,079.
Yet, despite the developments to date, there remain various shortcomings and drawbacks to many of the existing materials for cigarette filters. For example, it may be advantageous to avoid certain chemical and/or catalytic reactions that affect taste. Additionally, many of these materials may not be able to remove gas phase constituents from mainstream tobacco smoke.
Thus, there remains a continued interest in improved and more efficient methods and compositions for lowering certain gas phase constituents in the mainstream smoke of a cigarette during smoking. Preferably, such methods and compositions should not involve expensive or time consuming manufacturing and/or processing steps.